Why do you want to format it on the db? If you are pulling back the recordset with PHP you can format it then. I don't think MySql supplies any functions of that nature, but I could be mistaken. With PHP you can do a simple psuedo currency format, or you can get fancy with your PHP and HTML to format it any way you want. Of course, it then turns into a string. If you are going to be wanting to work with the numbers after displaying them you would need to put the numbers and displays in matching arrays or parse the numbers back out or something.
$number="$".number_format($number, 2, ".",",");
http://www.php.net/manual/en/function.number-format.php